Explain the following term with an example: Bidentate ligands.

Bidentate ligands are ligands that possess two donor atoms and can form two coordinate bonds with a single metal ion simultaneously.
Examples include:
$1$. Ethane$-1,2-$diamine $(NH_2CH_2CH_2NH_2)$: $A$ neutral bidentate ligand where both nitrogen atoms act as donor sites.
$2$. Oxalate ion $(C_2O_4^{2-})$: An anionic bidentate ligand where two oxygen atoms act as donor sites.